As agents for diabetes, heretofore, various biguanide compounds and sulfonylurea compounds have been used. However, biguanide compounds are not used at present, because these compounds induce undesirable side effects, such as lactic acidosis. Though having an excellent blood sugar-depressing effect, sulfonylurea compounds require care in use since they often induce grave hypoglycemia. Oxazole derivatives having a blood sugar-depressing effect and a sugar tolerance-improving effect are described in, for example, EP-92239, JP59-190979 and EP-382199.
The object of the present invention is to provide novel compounds which have an insulin secretion-promoting effect and a blood sugar-depressing effect, which are useful in agents for diabetes and which have low toxicity.